I got the 32-bit version running in VirtualBox OSE on an x86_64 Linux host without too much trouble. (network driver needs to be installed, the one from Win2003 works; guest additions complain so you need to "troubleshoot" them) The Installer for the x64 Version didn't start. Might work with the non-OSS 2.1 Version, which supposedly has better 64-bit support.